A graphic in the Siemens African Green City Index offers a side-by-side comparison of some key environmental factors in fifteen major African cities.
Overall, cities from the south and north perform the best. Cape Town, Durban, Johannesburg, Casablanca, Tunis and Accra all rank above average on the environmental scale. Pretoria generates the most waste. Johannesburg and Cairo consume the most water. Accra is one of the densest cities, and Tunis uses the most electricity.
See the full chart here.